U.S. patent application number 10/496461 was filed with the patent office on 2006-01-19 for process for the preparation of ethylene copolymers.
This patent application is currently assigned to Polimeri Eurpoa S.p.A.. Invention is credited to Paolo Biagini, Roberto Provera, Stefano Ramello, Maria Rivellini, Laura Santi, Roberto Santi, Stefano Santi.
Application Number | 20060014911 10/496461 |
Document ID | / |
Family ID | 11448643 |
Filed Date | 2006-01-19 |
United States Patent
Application |
20060014911 |
Kind Code |
A1 |
Biagini; Paolo ; et
al. |
January 19, 2006 |
Process for the preparation of ethylene copolymers
Abstract
A process is described for the preparation of ethylene
copolymers having a wide molecular weight distribution,
characterized in that it is carried out in the presence of meso-
and rac-stereoisomeric mixtures of metallocene compounds having
general formula (I), wherein A' and A'', the same or different, are
a radical of the .eta.?5.sub.L-tetrahydroindenyl type (Ia).
##STR1##
Inventors: |
Biagini; Paolo;
(Trecate-Novara, IT) ; Ramello; Stefano; (Novara,
IT) ; Provera; Roberto; (Vercelli, IT) ;
Santi; Roberto; (Novara, IT) ; Rivellini; Maria;
(Novara, IT) ; Santi; Stefano; (Novara, IT)
; Santi; Laura; (Novara, IT) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Polimeri Eurpoa S.p.A.
Via E. Fermi, 4
Brindisi
IT
72100
|
Family ID: |
11448643 |
Appl. No.: |
10/496461 |
Filed: |
November 18, 2002 |
PCT Filed: |
November 18, 2002 |
PCT NO: |
PCT/EP02/10639 |
371 Date: |
October 25, 2004 |
Current U.S.
Class: |
526/170 ;
526/943 |
Current CPC
Class: |
C08F 4/65912 20130101;
C08F 210/14 20130101; C08F 4/65927 20130101; C08F 210/16 20130101;
C08F 210/16 20130101; C07F 17/00 20130101; C08F 210/16 20130101;
Y10S 526/943 20130101 |
Class at
Publication: |
526/170 ;
526/943 |
International
Class: |
C08F 4/72 20060101
C08F004/72 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 2001 |
IT |
MI01A002516 |
Claims
1. A process for the preparation of ethylene copolymers having a
wide molecular weight distribution, characterized in that it is
carried out in the presence of meso- and rac-stereoisomeric
mixtures of metallocene compounds having general formula (I):
##STR9## wherein M is selected from zirconium, hafnium,; X.sub.1
and X.sub.2, the same or different, are selected from halogen,
amide, carboxy, alkoxy, carbamate, alkyl, aryl, hydrogen; A' and
A'', the same or different, are a radical of the
.eta..sup.5-tetrahydroindenyl type (Ia): ##STR10## wherein the
groups R.sub.5, R.sub.6, R.sub.7, R.sub.8, R.sub.9, R.sub.10, the
same or different, are selected from hydrogen, a C.sub.1-C.sub.8
aliphatic radical, a C.sub.5-C.sub.12 cycloaliphatic radical, a
C.sub.6-C.sub.14 aryl radical; the groups R.sub.1, R.sub.2,
R.sub.3, R.sub.4, the same or different, are selected from
hydrogen, a C.sub.1-C.sub.8 aliphatic radical, a C.sub.5-C.sub.12
cycloaliphatic radical, a C.sub.6-C.sub.14 aryl radical,
halogen.
2. The process according to claim 1, characterized in that M is
zirconium.
3. The process according to claim 1, characterized in that X.sub.1
and X.sub.2, the same or different, are selected from halogen,
C.sub.1-C.sub.7 hydrocarbyl radical, hydrogen.
4. The process according to claim 3, characterized in that X.sub.1
and X.sub.2 are chlorine.
5. The process according to claim 1, characterized in that R.sub.5,
R.sub.6, R.sub.7, R.sub.8, R.sub.9, R.sub.10, the same or
different, are selected from hydrogen, methyl, ethyl, phenyl.
6. The process according to claim 1, characterized in that the
groups R.sub.1, R.sub.2, R.sub.3, R.sub.4, the same or different,
are selected from hydrogen, methyl, benzyl, fluorine.
7. The process according to claim 6, characterized in that
R.sub.1=R.sub.2=R.sub.3=R.sub.4=H.
8. The process according to claim 1, characterized in that the
stereoisomeric mixture has a content of meso-compound ranging from
20 to 80%, the complement to 100 consisting of rac-compound.
9. The process according to claim 8, characterized in that the
stereoisomeric mixture consists of a 50/50 mixture of the two meso-
and rac-stereoisomers.
Description
[0001] The present invention relates to a process for obtaining
ethylene copolymers having a wide molecular weight
distribution.
[0002] More specifically, the present invention relates to a
process for obtaining ethylene/alpha-olefin copolymers
characterized in that it is carried out in the presence of one or
more metallocenes consisting of a racemic and meso mixture of
stereoisomers.
[0003] There has recently been a great deal of development in the
production of ethylene/alpha-olefin copolymers using catalysts
based on metallocenes. Metallocenes, in fact, offer the advantage
of having a greater catalytic activity than the traditional
Ziegler-Natta catalysts and are described as "single-site"
catalysts. Due to this "single-site" nature, the
ethylene/alpha-olefins copolymers produced in the presence of
metallocenes are usually uniform in their molecular structure. For
example, with respect to the traditional copolymers obtained with
Ziegler-Natta catalysts, copolymers from metallocenes have a
relatively narrow molecular weight distribution (MWD).
[0004] Although certain properties of the copolymers from
metallocenes are improved by narrow MWD, there are often
difficulties in processing these materials to give end-products or
films, with respect to the copolymers obtained with traditional
Ziegler-Natta catalysts.
[0005] A possibility for overcoming this drawback consists in
adding so-called "processing aids", i.e. substances suitable for
improving the processability, to the copolymers. This requires
additional processing and is therefore expensive.
[0006] Another approach consists in preparing compositions which
are mixtures of different polymeric materials, with the aim of
maximizing the best properties and contemporaneously minimizing
processability problems. This requires a further operation with an
increase in the cost of the materials produced. The following
patents relate to this mixture technology: U.S. Pat. No. 4,598,128;
U.S. Pat. No. 4,547,551; U.S. Pat. No. 5,408,004; U.S. Pat. No.
5,382,630; U.S. Pat. No. 5,382,631; U.S. Pat. No. 5,326,602; WO
94/22948 and WO 95/25141.
[0007] Another means of solving the problem of processability lies
in the development of various cascade processes, in which the
material is produced by a series of polymerizations under different
conditions, for example in a series of reactors. In this way, a
material is produced, which is very similar to a mixture and the
copolymers can have an improved processability, but these methods
are also costly and complicated with respect to the use of a single
reactor.
[0008] Another potentially feasible solution for improving the
processability consists in the use of multicomponent catalysts. In
certain cases, in fact, a metallocene catalyst and a Ziegler-Natta
catalyst supported on the same carrier or a catalyst consisting of
two metallocenes, are used. In this way, components having a
different molecular weight and composition are produced, in a
single reactor and adopting a single set of polymerization
conditions (see WO 95/11264 and EP 676,418). This approach however
is difficult from the point of view of process control and
preparation of the catalyst.
[0009] EP-A-955,304 describes a group of metallocene compounds with
a bridged structure useful in the preparation of .alpha.-olefin
(co) polymers.
[0010] It has now been found that it is possible to obtain ethylene
copolymers having a wide molecular weight distribution using a
single group of metallocenes selected from those described in the
above patent application.
[0011] In accordance with this, the present invention relates to
meso- and rac-stereoisomeric mixtures of metallocene compounds
having general formula (I): ##STR2## wherein M is selected from
titanium, zirconium, hafnium, preferably from zirconium and
hafnium, even more preferably M=Zr; X.sub.1 and X.sub.2, the same
or different, are selected from halogen, amide, carboxy, alkoxy,
carbamate, alkyl, aryl, hydrogen; they are preferably selected from
halogen, C.sub.1-C.sub.7 hydrocarbyl radical, hydrogen, and are
even more preferably chlorine; A' and A'', the same or different,
are a radical of the .eta..sup.5-tetrahydroindenyl type (Ia):
##STR3## wherein the groups R.sub.5, R.sub.6, R.sub.7, R.sub.8,
R.sub.9, R.sub.10, the same or different, are selected from
hydrogen, a C.sub.1-C.sub.8' aliphatic radical, a C.sub.5-C.sub.12
cycloaliphatic radical, a C.sub.6-C.sub.14 aryl radical, preferably
from hydrogen, methyl, ethyl, phenyl; the groups R.sub.1, R.sub.2,
R.sub.3, R.sub.4, the same or different, are selected from
hydrogen, a C.sub.1-C.sub.8 aliphatic radical, a C.sub.5-C.sub.12
cycloaliphatic radical, a C.sub.6-C.sub.14 aryl radical, halogen,
and are preferably hydrogen, methyl, benzyl, fluorine, even more
preferably hydrogen.
[0012] Said stereoisomeric mixtures have a meso- content ranging
from 20 to 80%, the complement to 100 consisting of rac-isomer.
[0013] In the preferred embodiment, the compound having general
formula (I) consists of an about 50/50 mixture of the two meso- and
rac-stereoisomers.
[0014] The compound having general formula (I) can be obtained by
the selective reduction of .eta..sup.5-1-indenyl complexes to give
the .eta..sup.5-1-tetrahydroindenyl complexes of the present
invention, preferably with hydrogen in the presence of platinum
oxide.
[0015] The reaction between anions of cyclopentadienyl, indenyl or
fluorenyl ligands and salts of transition metals, can generally
produce achiral metallocenes or metallocenes having various types
of stereoisomerism in relation to the symmetry of the ligands with
which the reaction is effected. In particular, ligands of the
bridged bis-indenyl type, with the bridge bound in positions 1 and
1', respectively, when used in the formation of metallocenes of
Group 4, can cause the formation of rac- and meso-bis (indenyl)
metal dichlorides, as the .pi. sides of each 1-substituted indenyl
ligand are enantiotopic. In this document, the planar chirality of
the complexes described refers to the definition of R. L. Halterman
contained in "Metallocenes synthesis reactivity applications" A.
Togni and R. L. Halterman editors, Wiley-VCH, Weinheim (1998),
volume 1, pages 456-469. According to this definition, the R or S
planar chirality is assigned on the basis of the configuration,
according to Cahn-Ingold-Prelog, of the carbon atom in position 1
of the ligand and considering the metal as individually bound to
all five carbon atoms of the cyclopentadienyl ring. In this way,
the chirality can be described as (p-R) or (p-S) or (1R) or (1S),
to emphasize that this definition of planar chirality is based on
position 1 of the ligand. For greater clarity, the concepts
described above are illustrated in Scheme 1, which shows the
various possibilities of obtaining bridged bis-tetrahydroindenyl
complexes with an o-benzylidene group bound in positions 1 and 1'.
##STR4## Scheme 1: Possibility of forming meso- and rac-complexes
by the reaction of ZrCl.sub.4 with dianions of
bis-tetrahydroindenyl ligands bridged in position 1, 1'.
[0016] The present invention also relates to a process for the
preparation of ethylene copolymers having a wide molecular weight
distribution, characterized in that it is carried out in the
presence of a meso- and rac-stereoisomeric mixture of metallocene
compounds having general formula (I): ##STR5## wherein M is
selected from titanium, zirconium, hafnium, preferably from
zirconium and hafnium; X.sub.1 and X.sub.2, the same or different,
are selected from halogen, amide, carboxy, alkoxy, carbamate,
alkyl, aryl, hydrogen; they are preferably selected from halogen,
C.sub.l-C.sub.7 hydrocarbyl radical, hydrogen, and are even more
preferably chlorine; A' and A'', the same or different, are a
radical of the .eta..sup.5-tetrahydroindenyl type (Ia): ##STR6##
wherein the groups R.sub.5; R.sub.6, R.sub.7, R.sub.8, R.sub.9,
R.sub.10, the same or different, are selected from hydrogen, a
C.sub.1-C.sub.8 aliphatic radical, a C.sub.5-C.sub.12
cycloaliphatic radical, a C.sub.6-C.sub.14 aryl radical, preferably
from hydrogen, methyl, ethyl, phenyl; the groups R.sub.1, R.sub.2,
R.sub.3, R.sub.4, the same or -different, are selected from
hydrogen, a C.sub.1-C.sub.8 aliphatic radical, a C.sub.5-C.sub.12
cycloaliphatic radical, a C.sub.6-C.sub.14 aryl radical, halogen,
and are preferably hydrogen, methyl, benzyl, fluorine, even more
preferably hydrogen.
[0017] In the preferred embodiment:
R.sub.1=R.sub.2=R.sub.3=R.sub.4=R.sub.5=R.sub.6=R.sub.7=R.sub.8=R.sub.9=-
R.sub.10=H; M=Zr.
[0018] Typical examples of metallocenes, consisting of meso- and
rac-stereoisomeric mixtures, having general formula (I), which can
be used for the production of ethylene copolymers according to the
present invention are:
[0019] o-benzylidenebis-(.eta..sup.5-1-tetrahydroindenyl)zirconium
dichloride;
[0020] o-benzylidenebis-(.eta..sup.5-1-tetrahydroindenyl)zirconium
dimethyl;
[0021] o-benzylidenebis-(.eta..sup.5-1-tetrahydroindenyl)zirconium
diacetate;
[0022] o-benzylidenebis-(.eta..sup.5-1-tetrahydroindenyl)zirconium
dimethoxide;
[0023] o-benzylidenebis-(.eta..sup.5-1-tetrahydroindenyl)zirconium
dihydride;
[0024] o-benzylidenebis-(.eta..sup.5-1-tetrahydroindenyl) zirconium
dibenzyl;
[0025] o-benzylidenebis- (.eta..sup.5-1-tetrahydro-3-methylindenyl)
zirconium dichloride;
[0026] o-benzylidenebis- (.eta..sup.5-1-tetrahydro-3-phenylindenyl)
zirconium dichloride;
[0027] o-benzylidenebis-(.eta..sup.5-1-tetrahydroindenyl)titanium
dichloride;
[0028] o-benzylidenebis-(.eta..sup.5-1-tetrahydroindenyl)titanium
dimethyl;
[0029] o-benzylidenebis- (.eta..sup.5-1-tetrahydroindenyl)hafnium
dichloride;
[0030] o-benzylidenebis-
(.eta..sup.5-1-tetrahydro-3-methylindenyl)hafnium dichloride;
[0031] o-benzylidenebis-
(.eta..sup.5-1-tetrahydro-3-phenylindenyl)hafnium dichloride;
[0032] o-benzylidene-3-methylbis- (.eta..sup.5-1-tetrahydroindenyl)
zirconium dichloride;
[0033] o-benzylidene-3-phenylbis- (.eta..sup.5-1-tetrahydroindenyl)
zirconium dichloride;
[0034] o-benzylidene-3-methylbis-
(.eta..sup.5-1-tetrahydroindenyl)zirconium dimethyl.
[0035] The catalytic system used in the present invention also
comprises, in addition to a meso- and rac-stereoisomeric mixture of
a metallocene having general formula (I), another component (which
we will call cocatalyst) selected from an alumoxane and compounds
having general formula (V) (Ra).sub.xNH.sub.4-xB(Rd).sub.4 (wherein
x is selected from 1, 2 or 3) or (VI) (Ra).sub.3PHB(Rd).sub.4, or
(VII) B(Rd).sub.3, or (VIII) (C.sub.6H.sub.5).sub.3CB(Rd).sub.4,
which, by reaction with a metallocene having general formula (I),
are capable of generating catalytic systems of an ionic nature. In
the above compounds having general formula (V), (VI), (VII) or
(VIII), the Ra groups, the same or different, are monofunctional
alkyl or aryl radicals, whereas Rd, the same or different, are
monofunctional aryl radicals, preferably partially or totally
fluorinated, even more preferably totally fluorinated.
[0036] As is known, the nature of the cocatalyst determines the
preparation procedure of the catalytic system. A general
description follows of two preparative methods of the catalytic
system, both well known to experts in the field.
[0037] According to a first method, the catalytic system is
prepared starting from one or more metallocenes having general
formula (I) and an alumoxane. The general term alumoxane indicates
an aluminum compound which can have a linear or cyclic structure.
The linear structure has general formula (IX)
(R.sub.e).sub.2--Al--O--[--Al--(R.sub.e)--O--].sub.p--Al(R.sub.e).sub.2,
whereas in its cyclic form it has general formula (X)
-[--O--Al(R.sub.e)--O--].sub.p+2-wherein the various R.sub.e, the
same or different, are selected from H, C.sub.1-C.sub.6 alkyl
radicals, C.sub.6-C.sub.18 aryl radicals; "p" is an integer from 2
to 50, preferably from 10 to 35. If the various R.sub.e are the
same, they are selected from methyl, ethyl, propyl, isobutyl, and
are preferably methyl.
[0038] If the various R.sub.e are different, they are preferably
methyl and hydrogen or alternatively methyl and isobutyl, hydrogen
and isobutyl being preferred.
[0039] The alumoxane can be prepared according to various methods
known to experts in the field. One of the methods comprises, for
example, the reaction of an aluminum alkyl and/or an alkylaluminum
hydride with water (gaseous, solid, liquid or bound, such as
crystallization water, for example) in an inert solvent, for
example toluene. For the preparation of an alumoxane having
different R.sub.e alkyl groups, two different aluminumtrialkyls
(AlR.sub.3+AlR'.sub.3) are reacted with water (see S. Pasynkiewicz,
Polyhedron 9 (1990) 429-430 and EP-A-302,424).
[0040] The exact nature of the alumoxane is not known; however
toluene solutions of methyl-alumoxane are commercially available,
such as the product Eurecene 5100 10T of Witco whose concentration
in active aluminum is provided, thus considerably facilitating its
use.
[0041] The catalytic system is prepared by adding a hydrocarbon
solution at 10% by weight of alumoxane to the mixture of
anhydrified monomers, previously charged into the polymerization
reactor. The mixture is brought to the desired temperature and one
or metallocenes selected from those having general formula (I), are
then added, in such a quantity as to obtain a total concentration
ranging from 10.sup.-8 to 10.sup.-4 molar (depending on its
activity), and with a molar ratio aluminum/metallocene ranging from
2.times.10.sup.2 to 2.times.10.sup.4. In this way, the catalytic
system is defined as being "prepared in situ".
[0042] Alternatively, the metallocene, or mixture of metallocenes,
can be pre-activated with the alumoxane before its use in the
polymerization phase. In this case, one or more metallocenes having
general formula (I) are dissolved in an inert hydrocarbon solvent,
preferably aliphatic or aromatic, even more preferably toluene, so
that the total concentration ranges from 10.sup.-1 to 10.sup.-4
molar. The toluene solution of alumoxane is then added so that the
molar ratio aluminum/metallocene ranges from 2.times.10.sup.2 to
2.times.10.sup.4. The components are left to react for a time
ranging from a few minutes to 60 hours, preferably from 5 to 60
minutes, at a temperature ranging from -78.degree. C. to
+100.degree. C., preferably from 0.degree. C. to 70.degree. C. This
preparation procedure of the catalytic system is commonly defined
as "preformation". At the end of the preformation time, the mixture
containing the catalytic system is added to the mixture of monomers
previously prepared in the polymerization reactor, so that the
final concentration of the metallocene in the reactor ranges from
10.sup.-8 to 10.sup.-4 moles/litre.
[0043] According to a second method, the catalytic system is
prepared again starting from one or more metallocenes having
general formula (I) and a cocatalyst having general formula (V),
(VI), (VII) or (VIII). The operating procedure depends, in this
case, on the nature of the X groups bound to M in general formula
(I).
[0044] When X is equal to H or an alkyl radical, the catalytic
system is prepared by adding one or more metallocenes having
general formula (I) to the mixture of monomers previously prepared
so that the total concentration ranges from 10.sup.-8 to 10.sup.-4
moles/litre. The mixture is brought to the desired temperature and
a compound is added as cocatalyst, selected from those having
general formula (V), (VI), (VII) or (VIII) as described in
EP-A-277,004, in such a concentration that the total molar ratio
cocatalyst/metallocene ranges from 0.1 to 10, preferably from 1 to
3.
[0045] When X is different to H or a hydrocarbyl radical, the
catalytic system consists of one or more metallocenes having
general formula (I), an alkylating compound selected from aluminum
trialkyl, magnesium dialkyl and lithium alkyl, or other alkylating
agents well known to experts in the field, and any one of the
compounds having general formula (V), (VI), (VII) or (VIII) or one
of their mixtures, as described in EP-A-612,769. The formation
procedure of the catalytic system comprises premixing of the
metallocene compound having general formula (I) with a suitable
alkylating agent in aliphatic or aromatic hydrocarbon solvents, or
their mixtures, at a temperature ranging from -20 to +100.degree.
C., preferably from 0.degree. C. to 60.degree. C. and even more
preferably from +20.degree. C. to +50.degree. C., for a time
varying from 1 minute to 24 hours, preferably from 2 minutes to 12
hours, even more preferably from 5 minutes to 2 hours.
[0046] The molar ratio between the alkylating compound and the
compound having general formula (I) can vary from 1 to 1000,
preferably from 10 to 500, even more preferably from 30 to 300.
[0047] The mixture is then put in contact with a compound having
general formula (V), (VI), (VII) or (VIII) at the temperature
specified above, for a time ranging from 1 minute to 2 hours,
preferably from 2 minutes to 30 minutes, and is subsequently fed to
the polymerization reactor. The molar ratio between the compound
having general formula (V), (VI), (VII) or (VIII) and the
metallocene (I) can vary from 0.1 to 10, preferably from 1 to
3.
[0048] Regardless of the method used for the preparation of the
catalytic system, the reaction between the metallocene having
general formula (I) and the cocatalyst can be carried out with or
without varying quantities of one or all of the monomers to be
polymerized. When small quantities of the monomers to be
polymerized are present, i.e. with molar ratios monomer/metallocene
ranging from 10 to 1000, what is defined in the known art as
prepolymerization takes place, wherein small quantities of solid
polymers are formed, which englobe almost all of the components of
the catalytic system. This polymer/catalytic system suspension
still shows a high catalytic activity and can be used to polymerize
high quantities of monomers with an improvement in the
morphological characteristics of the polymer obtained.
[0049] The catalytic systems of the present invention are generally
used in very low molar concentrations, ranging from 10.sup.-8 to
10.sup.-4, expressed in metallocene having general formula (I).
Although extremely diluted, these catalytic systems are
characterized by a very high activity, ranging from 500 to 10000 Kg
of polymer per gram of transition metal per hour of
copolymerization. To obtain these activities at the above
concentrations, however, the catalytic system must be carefully
protected from poisons which are possibly present, also in parts
per million, in the monomers, above all propylene, and in the
solvents used in the polymerization reaction. This result can be
obtained by the use, in the polymerization environment, of
substances which are particularly effective in eliminating
impurities characterized by the presence of active hydrogens, such
as aluminum trialkyls, in particular aluminum trimethyl, aluminum
triethyl, aluminum triisobutyl and aluminum diisobutylmonohydride.
These substances do not directly take part in the catalytic process
but are capable of effectively capturing the above poisons if used
in concentrations of about 10.sup.-3-10.sup.-4 molar in the
polymerization environment.
[0050] Molecular weight control agents can be used in a combination
with the above cocatalysts. Examples of these molecular weight
control agents comprise hydrogen, aluminum hydride compounds, alkyl
compounds of zinc and other known chain transfer agents.
[0051] The catalytic system of the present invention can be used in
any known polymerization process (for example gas phase, solution,
slurry) of monomers polymerizable by addition, comprising
ethylenically unsaturated monomers, acetylene compounds, conjugated
or non-conjugated dienes, polyenes and relative mixtures. Preferred
monomers include olefins, for example .alpha.-olefins having from 2
to 30 carbon atoms, preferably from 2 to 8 carbon atoms, and
relative combinations of two or more of these .alpha.-olefins.
Examples of particularly convenient .alpha.-olefins are ethylene,
propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene,
1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene,
1-tridecene, 1-tetradecene and relative mixtures, as well as
vinyl-terminated oligomeric chains or polymeric reaction products
formed during the polymerization. The .alpha.-olefins are
preferably ethylene, propene, 1-butene, 4-methyl-1-pentene,
1-hexene, 1-octene and combinations of ethylene and/or propene with
one or more other .alpha.-olefins, and are even more preferably
ethylene, propene, 1-butene, 1-hexene, 1-octene and relative
combinations of two or more of these.
[0052] The polymerization is generally carried out under conditions
well known in literature for polymerization reactions of the
Ziegler-Natta or Kaminsky-Sinn type. The polymerization can be
carried out in suspension, in solution, in slurry or in gas phase,
batchwise or in continuous.
[0053] Examples of these well known polymerization processes are
provided in WO 88/02009, U.S. Pat. No. 5,084,534; U.S. Pat. No.
5,405,922; U.S. Pat. No. 4,588,790; U.S. Pat. No. 5,032,652. The
preferred polymerization temperatures range from 0 to 250.degree.
C., whereas the preferred polymerization pressures range from
atmospheric pressure to 3000 atmospheres.
[0054] The process of the present invention is preferably carried
out in a single reactor.
[0055] In most polymerization reactions, the molar ratio
catalyst/polymerizable compounds ranges from 10.sup.-12:1 to
10.sup.-11:, more preferably 10.sup.-5:1.
[0056] In the case of polymerization in solution and/or suspension,
convenient solvents, consisting of inert liquids, comprise linear
and branched hydrocarbons such as, for example, propane, butane,
isobutane, pentane, hexane, heptane, octane, iso-octane, and
relative mixtures; cyclic hydrocarbons, also variably alkyl
substituted, such as cyclohexane, cycloheptane, methylcyclohexane,
methylcyclopentane and relative mixtures; perfluorinated
hydrocarbons such as C.sub.4-C.sub.10 perfluorinated alkanes;
aromatic hydrocarbons and alkylsubstituted aromatic hydrocarbons
such as benzene, toluene, xylene and relative mixtures. Convenient
solvents are also those which comprise liquid olefins that can also
act as monomers or comonomers, such as propylene, 1-butene,
butadiene, cyclopentene, 1-hexene, 1-heptene, 3-methyl-1-pentene,
4-methyl-1-pentene, 1,4-hexadiene, 1,7-octadiene, 1,9-decadiene,
1-octene, 1-decene, styrene, divinylbenzene, ethylidene-norbornene,
allylbenzene, vinyltoluene, 4-vinylcyclohexene, vinylcyclohexane,
and relative mixtures.
[0057] One of these polymerization processes comprises putting one
or more a-olefins in contact, optionally in a solvent, with a
catalyst in one or more reactors in continuous of the stirred or
tubular-type, see for example U.S. Pat. No. 5,272,236 and U.S. Pat.
No. 5,278,272.
[0058] The process of the present invention can also be
advantageously used in the (co)polymerization in gas phase of
olefins. Polymerization processes of olefins in gas phase are well
known in literature, and in particular the homopolymerization and
copolymerization of ethylene and propylene, and the
copolymerization of ethylene with higher .alpha.-olefins, such as
1-butene, 1-hexene, 4-methyl-1-pentene. The above processes are
commercially used on a wide scale for the production of high
density polyethylene (HDPE), medium density polyethylene (MDPE),
linear low density polyethylene (LLDPE) and polypropylene.
[0059] The process in gas phase used can be, for example, of the
type adopting, as polymerization reaction zone, a mechanically
stirred bed or a gas fluidized bed. A large number of patents
describe processes in gas phase, see, for example, U.S. Pat. No.
4,588,790; U.S. Pat. No. 4,543,399; U.S. Pat. No. 5,352,749;
EP-A-659,773; EP-A-692,500; WO 94/29032; WO 94/25497.
[0060] The ethylene copolymers obtained with the process of the
present invention have the characteristic of having a quantity of
comonomer of over 50% (with respect to the total content present)
concentrated at 50% by weight of the fractions with a higher
molecular weight than the copolymer itself.
[0061] The following examples are provided for a better
understanding of the present invention.
EXAMPLES
[0062] The analytical techniques and characterization methods
listed and briefly described below were used in the following
examples.
[0063] The characterization by .sup.1H-NMR and .sup.13C-NMR
spectroscopy, mentioned in the following examples, was effected on
a nuclear magnetic resonance spectrometer mod. Bruker AM-300.
[0064] The characterization of the complexes, by means of mass
spectrometry, was effected using a Finnigan Mat 8400 double focus,
inverse geometry, spectrometer.
[0065] The molecular weight measurement of the olefinic polymers
was carried out by means of Gel-Permeation chromatography (GPC).
The analyses of the samples were effected in
1,2,4-trichloro-benzene (stabilized with Santonox) at 135.degree.
C. with a WATERS 150-CV chromatograph using a Waters differential
refractometer as detector.
[0066] The chromatographic separation was obtained with a set of
.mu.-Styragel HT columns (Waters) of which three with pore
dimensions of 10.sup.3, 10.sup.4, 10.sup.5 .ANG., and two with pore
dimensions of 10.sup.6 .ANG., establishing a flow-rate of the
eluant of 1 ml/min.
[0067] The data values were acquired and processed by means of
Maxima 820 software version 3.30 (Millipores); the number average
molecular weight (Mn) and weight average molecular weight (Mw)
calculation was effected by means of universal calibration,
selecting polystyrene standards with molecular weights within the
range of 6,500,000-2,000, for the calibration.
[0068] The content of units deriving from 1-hexene or 1-octene in
the polymers was determined by means of the known techniques based
on .sup.13C-NMR spectroscopy.
[0069] The commercial reagents listed below were used in the
preparations described in the examples: TABLE-US-00001 ***
n-butyl-lithium (LiBu) 1.6 M in hexane ALDRICH *** zirconium
tetrachloride (ZrCl.sub.4) FLUKA *** methylalumoxane (MAO)
(Eurecene 5100 10T, 10% weight/volume of Al in toluene) WITCO ***
platinum dioxide (PtO.sub.2) ALDRICH *** molecular sieves (3A)
ALDRICH
[0070] The reagents and/or solvents used and not indicated above
are those commonly adopted in laboratories and on an industrial
scale and can be easily found at the usual commercial operators
specialized in the field.
EXAMPLE
Synthesis of o-benzylidenebis-(.eta..sup.5-1-indenyl)-zirconium
dichloride (III).
[0071] The procedure described herein has a few variations with
respect to that provided in EP-A-955,304. ##STR7## obtained as
described in EP-A-955,304, and 100 ml of anhydrous ethyl ether are
charged, under an atmosphere of argon, into a 250 ml tailed
test-tube, equipped with a magnetic stirrer. 21 ml of LiBu (1.6 M
in hexane) (33.6 mmoles) are added dropwise, at room temperature,
to the pale yellow solution thus obtained and the mixture is kept
under stirring for about 12 h. At the end, the volume of the
reaction mixture is reduced to about 20 ml, most of the solvent
being removed at reduced pressure, and 50 ml of anhydrous n-hexane
are then added. A suspension is immediately formed, which is
filtered; the solid is collected and subsequently washed with
n-hexane (3.times.10 ml). It is dried under vacuum (about 10 Pa)
and the dilithium derivative having formula (IIa) thus obtained, is
transferred, under an atmosphere of argon, to a 100 ml tailed
test-tube containing 50 ml of anhydrous toluene. 4.03 g of
ZrCl.sub.4 (17.3 mmoles) are added to the suspension thus obtained
and the reaction mixture is then left under stirring at room
temperature for about 16 h, after which it is filtered on a porous
septum and the mother liquor containing the desired product is
collected. The residue is washed again with toluene (3.times.10 ml)
and the washing water is joined to the mother liquor. The toluene
solution thus obtained is dried, eliminating the solvent at reduced
pressure, and the yellow solid obtained is further dried under
vacuum (10 Pa) for 6 h. 4.83 g of
o-benzylidenebis-(.eta..sup.5-1-indenyl)zirconium dichloride (III)
are obtained (72% yield). NMR analysis reveals that there are two
isomers (meso- and rac-) in the product, in a ratio of about 50/50.
.sup.1H-NMR (CDCl.sub.3, .delta. ppm rel. to TMS): rac-isomer: 4.42
(1H, d, J 17.07), 4.66 (1H, d, J 17.06), 5.69 (1H, d, J 3.45), 6.50
(1H, d, J 3.30), 6.52 (1H, d, J 3.49), 6.64(1H, d, J 3.49),
7.10-7.40 (8H, m), 7.40-7.70 (4H, m); meso-isomer: 4.58 (2H, s),
6.27 (1H, d, J 3.48), 6.68 (1H, d, J 2.96), 6.74 (1H, d, J 3.53),
6.82 (1H, d, J 3.45), 7.10-7.40 (m, 8H), 7.40-7.70 (4H, m). DCI-MS:
m/z 478 (negative ions, greatest intensity peak of the
cluster).
EXAMPLE 2
[0072] Synthesis of
o-benzylidenebis-(.eta..sup.5-1-tetrahydroindenyl) zirconium
dichloride (IV). ##STR8##
[0073] The following products are charged in order into an 80 ml
steel autoclave: 1.17 g of o-benzylidenebis-(.eta..sup.5-1-indenyl)
zirconium dichloride (III) (2.4 mmoles), prepared as described in
Example 1, 0.045 g of PtO.sub.2 (0.2 nmoles), 1 g of molecular
sieves (3A) and 30 ml of CH.sub.2Cl.sub.2. Hydrogen is then charged
up to a pressure of 0.5 MPa, maintaining the apparatus at room
temperature, and the mixture is left under stirring for about 3 h,
care being taken to keep the hydrogen pressure constant. At the
end, the suspension is filtered and the mother liquor recovered.
The solvent is completely removed at reduced pressure and 30 ml of
n-hexane are added to the residual solid; any possible insoluble
products are removed by filtration, the solvent is then removed at
reduced pressure and the extremely light-yellow residual solid is
dried under vacuum (10 Pa) for 24 h. 0.73 g of
o-benzylidenebis-(.eta..sup.5-1-tetrahydro-indenyl)-zirconium
dichloride (IV) are thus obtained (yield 62%). NMR analysis reveals
that there are two isomers (meso- and rac-) in the product, in a
ratio of about 50/50.
[0074] .sup.1H-NMR (C.sub.6DC.sub.6, .delta. ppm rel. to TMS):
rac-isomer: 1.5-3.3 (16H, m), 3.84 (1H, d, J=17.26), 4.06 (1H, d,
J=17.25), 5.37 (.sup.1H, d, J=3.14 Hz), 5.83 (1H, d, J=3.18 Hz),
6.09 (1H, d, J=3.13 Hz), 6.32 (1H, d, J=3.16 Hz), 7.30-7.41 (4H,
m); meso-isomer: 1.5-3.3 (16H, m), 3.89 (2H, s), 5.62 (1H, d,
J=3.30 Hz), 5.99 (1H, d, J=3.15 Hz), 6.13 (1H, d, J=3.24 Hz), 6.40
(1H, d, J=3.13 Hz), 7.20-7.40 (4H, m). [0075] DCI-MS: m/z 486
(negative ions, greatest intensity peak of the cluster).
EXAMPLE 3
[0075] Preparation of rac-o-benzylidenebis-(.eta..sup.5-1-indenyl)
zirconium dichloride (IIIr) and
meso-o-benzylidenebis-(.eta..sup.5-1-indenyl) zirconium dichloride
(IIIm).
[0076] 4.8 g of the complex (III) (10 mmoles) in which the two
(meso- and rac-) isomers are present in a ratio of about 50/50,
obtained as described in Example 1, and 20 ml of toluene, are
charged, in an atmosphere of argon, into a 100 ml tailed test-tube,
equipped with a magnetic stirrer. The suspension is filtered and
the solid collected is dried under vacuum (about 10 Pa). 1.2 g of
rac-o-benzylidenebis-(.eta..sup.5-1-indenyl) zirconium dichloride
(IIIr) are thus obtained, having a stereoisomeric purity of 95%,
determined by means of .sup.1H-NMR.
[0077] The solvent is removed from the filtrate at reduced pressure
and the residual solid is dried under vacuum (10 Pa). 3.6 g of
meso-o-benzylidenebis-(.eta..sup.5-1-indenyl) zirconium dichloride
(IIIm) are thus obtained, having a stereoisomeric purity of 67%,
determined by means of .sup.1H-NMR.
EXAMPLE 4
Synthesis of
rac-o-benzylidenebis-(.eta..sup.5-1-tetrahydro-indenyl) zirconium
dichloride (IVr).
[0078] The following products are charged in order into an 80 ml
steel autoclave: 1.36 g of
rac-o-benzylidenebis-(.eta..sup.5-1-indenyl) zirconium dichloride
(IIIr) (2.9 mmoles), 0.047 g of PtO.sub.2 (0.2 mmoles), 1 g of
molecular sieves (3A) and 30 ml of CH.sub.2Cl.sub.2. Hydrogen is
then charged up to a pressure of 0.5 MPa, maintaining the apparatus
at room temperature, and the mixture is left under stirring for
about 3 h, care being taken to keep the hydrogen pressure constant.
At the end, the suspension is filtered and the mother liquor
recovered. The solvent is completely removed at reduced pressure
and 30 ml of n-hexane are added to the residual solid; any possible
insoluble products are removed by filtration, the solvent is then
removed at reduced pressure and the light-yellow residual solid is
dried under vacuum (10 Pa) for 12 h. 0.96 g of
rac-o-benzylidenebis-(.eta..sup.5-1-tetrahydro-indenyl)-zirconium
dichloride (IVr) are thus obtained (yield 70%), having a
stereoisomeric purity of 95%, determined by means of
.sup.1H-NMR.
.sup.1H-NMR (CDCl.sub.3, .delta. ppm rel. to TMS): 1.5-3.3 (16H,
m), 3.84 (1H, d, j 17.26), 4.06 (1H, d, J 17.25), 5.37 (1H, d, J
3.14 Hz), 5.83 (1H, d, J 3.18 Hz), 6.09 (1H, d, J 3.13 Hz), 6.32
(1H, d, J 3.16 Hz), 7.30-7.41 (4H, m).
[0079] DCI-MS: m/z 486 (negative ions, greatest intensity peak of
the cluster).
EXAMPLE 5
[0079] Synthesis of
meso-o-benzylidenebis-(T'.sup.5-1-tetrahydro-indenyl) zirconium
dichloride (IVm).
[0080] The following products are charged in order into an 80 ml
steel autoclave: 1.36 g of
meso-o-benzylidenebis-(.eta..sup.5-1-indenyl) zirconium dichloride
(IIIm) (2.4 mmoles), 0.048 g of PtO.sub.2 (0.2 mmoles), 1 g of
molecular sieves (3A) and 30 ml of CH.sub.2Cl.sub.2. Following a
procedure which is completely analogous to that described in
Example 3, 0.83 g of meso-o-benzylidenebis-
(.eta..sup.5-1-tetrahydro-indenyl) zirconium dichloride (IVm) are
recovered at the end (yield 72%), having a stereoisomeric purity of
80%, determined by means of .sup.1H-NMR.
.sup.1H-NMR (CDCl.sub.3, .delta. ppm rel. to TMS): 1.5-3.3 (16H,
m), 3.89 (2H, s), 5.62 (1H, d, J=3.30 Hz), 5.99 (1H, d, J=3.15 Hz),
6.13 (1H, d, J=3.24 Hz), 6.40 (1H, d, J=3.13 Hz), 7.20-7.40 (4H,
m).
[0081] DCI-MS: m/z 486 (negative ions, greatest intensity peak of
the cluster).
EXAMPLES 6 to 20
[0081] Copolymerization of ethylene/1-hexene (or 1-octene) using
MAO as cocatalyst.
[0082] Examples 6 to 11 refer to a series of copolymerization tests
for the preparation of modified polyethylenes based on
ethylene/1-hexene, whereas Examples 17 to 20 refer to a series of
copolymerization tests for the preparation of modified
polyethylenes based on ethylene/l-octene, carried out using a
catalytic system comprising the metallocene complex, obtained as
described above in Example 2 and methylalumoxane (MAO) as
cocatalyst. In Examples 12 to 16, a comparison is made in the
production of ethylene/1-hexene copolymers using a catalytic system
consisting of one of the metallocene complexes, prepared according
to Examples 1, 3, 4 or 5 and MAO as cocatalyst. The specific
polymerization conditions of each example and the results obtained
are specified in Tables (I) and (II) below, which indicate in
succession, the reference example number, the metallocene complex
used, the quantity of zirconium used, the atomic ratio between the
aluminum in the MAO and zirconium in the metallocene, the
polymerization temperature, the concentration of comonomer
(1-hexene or 1-octene) present in liquid phase expressed in molar
percentage, the activity of the catalytic system expressed as
kilograms of polymer per gram of metallic zirconium per hour:
(kg.sub.pol./g.sub.zrxh), the relative quantity, by weight, of the
monomeric units (C.sub.6 or C.sub.8) in the polymer, the weight
average molecular weight M.sub.w and M.sub.w/M.sub.n molecular
weight dispersion.
[0083] The polymerization is carried out in an 0.5 litre pressure
reactor, equipped with a magnetic drag anchor stirrer and external
jacket connected to a heat exchanger for the temperature control.
The reactor is previously flushed by maintaining under vacuum (0.1
Pascal) at a temperature of 80.degree. C. for at least 2 hours.
[0084] 130 g of anhydrous n-heptane and the comonomer (1-hexene or
1-octene) are charged into the reactor, at 23.degree. C., in such a
quantity as to obtain the molar concentration indicated in the
corresponding column in Tables (I) and (II) below. The reactor is
then brought to the desired polymerization temperature
(40-80.degree. C.) and "polymerization grade" gaseous ethylene is
fed by means of a plunged pipe until the desired total equilibrium
pressure of 1.1 MPa is reached, as specified in Tables (I) and (II)
below.
[0085] The MAO, as a 1.5 M solution (as Al) in toluene, and the
desired quantity of one of the above metallocene complexes as a
toluene solution having a concentration generally ranging from
3.times.10.sup.-4 to 1.times.10.sup.-3 M, are charged into a
suitable tailed test-tube, maintained under nitrogen. The catalyst
solution thus formed is kept at room temperature for a few minutes
and is then transferred under a stream of inert gas to a metal
container from which, due to an over-pressure of nitrogen, it
enters the reactor.
[0086] The polymerization reaction is carried out at the desired
temperature, care being taken to keep the total pressure constant
by continuously feeding ethylene to compensate the part which has
reacted in the meantime. After 30 minutes, the ethylene feeding is
interrupted and the polymerization is stopped by the addition of 10
ml of ethyl alcohol. After opening the autoclave, its contents are
poured into a suitable glass container, containing 500 ml of ethyl
alcohol. The suspension obtained is kept under stirring for about
30 minutes, in order to obtain the complete coagulation of the
polymeric material present in the reaction mixture. Finally, the
polymer is recovered by decanting or by filtration, depending an
the morphology obtained and, after washing with two 100 ml portions
of ethyl alcohol, it is dried at 60.degree. C., at a reduced
pressure of 1000 Pa, for at least 8 hours, in order to completely
eliminate any possible residual monomers. The solid thus obtained
is weighed and the activity of the catalyst is calculated as
described above. The content of the different 1-hexene or 1-octene
monomeric units, depending on the cases, is measured on the dried
and homogenized solid, by means of the known techniques based on
.sup.13C-NMR spectroscopy, together with the weight average
(M.sub.w) and number average (M.sup.n) molecular weight. The
overall results are indicated in Tables I and II. TABLE-US-00002
TABLE I ehtylene/1-hexene copolymerization according to Examples 6
to 16.sup.(a). Complex IV forms part of the present invention, the
others being provided for comparative pur- poses. Zr Al/Zr C.sub.6
(feed) Activity C.sub.6 (pol.) Ex. (mol. .times. moles/ T (%
kg.sub.pol./ (% M.sub.w Nr. Compl. 10.sup.-8) moles (.degree. C.)
moles) g.sub.Zr.times. h weight) (.times. 10.sup.3) M.sub.w/M.sub.n
6 IV 0.11 4060 80 6.6 3856 5.4 162 4.1 7 IV 0.46 3799 60 6.6 2412
6.0 263 3.9 8 IV 0.57 3776 40 6.6 544 7.3 463 3.9 9 IV 0.46 3799 60
6.6 2399 5.8 284 3.7 10 IV 0.46 3799 60 9.6 1152 7.7 207 3.9 11 IV
0.458 3799 60 12.4 484 8.9 153 4.3 12 IIIm 0.31 3742 80 6.6 2481
5.8 222 2.2 13 IIIr 0.15 4833 80 6.6 3114 6.0 181 2.3 14 III 0.19
4088 80 6.6 2815 5.8 211 2.4 15 IVr 0.18 5576 80 6.6 4318 6.9 175
1.9 16 IVm 0.23 5065 80 6.6 2064 3.1 94 2.2 .sup.(a)Each example
was carried out at an ethylene pressure equal to 1.1 MPa and using
n-heptane as solvent.
Comments on Table I
[0087] As can be seen from the data summarized in Table I, the use
of o-benzylidenebis- (.eta..sup.5-1-tetrahydroindenyl) zirconium
dichloride (IV), in the production of ethylene/1-hexene copolymers
(Examples 6-11), allows products to be obtained, having molecular
weight distribution (M.sub.w/M.sub.n) values ranging from 3.7 to
4.3. This in itself is already an advantage with respect to the use
of the analogous derivative with non-hydrogenated indenyl ligands
o-benzyli-denebis-(.eta..sup.5-1-indenyl) zirconium dichloride
(III), but on analyzing the comparative examples (12-16) in more
detail, other positive aspects emerge, associated with the use of
the complex (IV). The meso- and rac-stereoisomers (IIIm and IIIr,
respectively), obtained according to the procedure described in
Example 3, of which the complex
o-benzylidenebis-(.eta..sup.5-1-indenyl) zirconium dichloride (III)
consists, have a very similar behaviour in the production of
ethylene/1-hexene copolymers (Examples 12 and 13) with respect to
the quantity of comonomer inserted and the weight average molecular
weight value, even if, considering the catalytic activity, there is
still a certain difference in favour of the rac-isomer. There is a
radical and unexpected change in the case of the analogous meso-
and rac-stereoisomers (IVm and IVr, respectively), obtained
according to the procedure described in Examples 4 and 5, of which
the complex o-benzylidenebis-(.eta..sup.5-1-tetrahydro-indenyl)
zirconium dichloride (IV) consists. As can be clearly seen, in
fact, from Examples 15 and 16, the stereoisomer IVr shows a greater
catalytic activity, contemporaneously providing polymers with a
higher content of comonomer and with much higher weight average
molecular weight values, with respect to the IVm stereoisomer. The
use of the complex
o-benzylidenebis-(.eta..sup.5-1-tetrahydro-indenyl) zirconium
dichloride (IV), prepared as described in Example 2, therefore
makes it possible to obtain ethylene/1-hexene copolymers which are
characterized, in addition to a wide molecular weight distribution,
as already mentioned above, also by a heterogeneous distribution of
the comonomer with respect to the molecular weight, most of the
1-hexene being concentrated in the polymer fractions with a higher
molecular weight (Examples 6 - 11). These characteristics give the
copolymers thus obtained a considerably improved processability
with respect to analogous products having the same content of
comonomer, prepared with other catalytic systems. Furthermore, the
use of the complex
o-benzyli-denebis-(.eta..sup.5-1-tetrahydro-indenyl) zirconium
dichloride (IV) allows, under the same experimental conditions,
catalytic activities to be obtained, which are about 30% higher
with respect to the analogous complex with non-hydrogenated indenyl
ligands (III), thus reducing the catalysis costs. TABLE-US-00003
TABLE II ethylene/1-octene copolymerization according to Examples
17 to 20.sup.(a). Zr Al/Zr C.sub.8 (feed) Activity C.sub.8 (pol.)
Ex. (mol. .times. moles/ T (% kg.sub.pol./ (% M.sub.w Nr. Compl.
10.sup.-6) moles (.degree. C.) moles) g.sub.Zr.times. h weight)
(.times. 10.sup.3) M.sub.w/M.sub.n 17 IV 0.46 3799 60 5.3 2172 8.9
248 3.9 18 IV 0.46 3799 60 10.2 1276 11.1 190 4.4 19 IV 0.18 3974
80 5.3 3011 6.1 155 4.5 20 IV 1.09 1593 80 10.2 1477 13.0 91 4.9
.sup.(a)Each example was carried out at an ethylene pressure equal
to 1.1 MPa and using n-heptane as solvent.
Comments on Table II
[0088] The data provided in Table II demonstrate that the general
characteristics of the copolymers obtained with the complex
o-benzylidenebis- (.eta..sup.5-1-tetrahydro-indenyl) zirconium
dichloride (IV), widely illustrated above, also remain unaltered
for the copolymerization of ethylene/1-octene. Also in this case,
in fact, the copolymers described all have molecular weight
distributions (M.sub.w/M.sub.n) higher than 3.9, regardless of the
temperature at which they were obtained and the quantity of
comonomer fed.
* * * * *